1. Field of the Invention
The invention, applies generally to tape dispensing and application equipment and, more particularly, to a bi-directional tape applicator head with dual tape supply.
The invention was developed primarily for use in the field of composite technology. In particular, the invention is used in constructing structural and aerodynamic parts of an aircraft. However, the invention can also be used for the construction of structural and aerodynamic parts for craft other than aircraft, for the construction of missiles, satellites, automobile bodies, rail cars, ships and the like.
According to composite technology, a resin preimpregnated tape having, for example, fiberglass filaments is utilized with or without additional resin adhesive to construct the particular part desired. The final part is built-up of a successive application of layers of the tape to a working surface as, for example, a mandrel. The resulting part is light in weight and highly load redundant, so it is more desirable than a corresponding part made from traditional materials such as steel, aluminum, etc.
2. Prior Art
U.S. Pat. No. 4,259,144 discloses a bi-directional tape applicator head for dispensing and compacting tape in two opposing directions onto a working surface. The tape is fed vertically between two spaced, symmetrically-orientated dispensing blocks onto the working surface. As the head moves in one direction, one of these blocks engages the tape and imparts a tension to the tape to draw the tape past the dispensing block to the working surface. At the end of the tape laying pass, the directional motion of the head is reversed, causing the tape to be disengaged from the one dispensing block and engaged with the other dispensing block, which folds the tape back on itself and compacts it against the previously laid layer of tape. The tape applicator head includes a tape shearing mechanism disposed between the tape supply and the dispensing blocks shearing the tape upon completion of the tape laying operation. The tap applicator head also includes a tape advancement mechanism for feeding tape from the tape supply between the two dispensing blocks onto the working surface to initiate a tape laying operation. The tape advancement mechanism includes a cam roller and an idler roller which are mounted adjacent to each other on opposite sides of the tape. The cam roller has an outermost surface which is semicircular in cross section, and which engages the tape as the cam roller is rotated. The circumference of this semicircular portion is at least equal to the distance between the end of the tape and the working surface, so that as the cam roller is rotated, tape will be advanced through the two dispensing blocks onto the working surface.
In this known tape applicator head, tape distortions such as wrinkles or folds, can frequently be introduced to the tape as it is folded back upon itself during reversal of the tape placement. Also, since both of the dispensing blocks are disposed the same distance from the working surface, difficulty can be encountered in laying different lengths of tape to form a contoured part of varying thickness, in that the block not engaged with the tape being layed may engage with the end of a previously laid tape layer. Also, the tape advancement mechanism of this known tape applicator head is suitable only for vertical advancement of the tape, since it includes no means for holding and guiding the tape through the shearing mechanism and between the two dispensing blocks.
In U.S. Pat. No. 4,234,374 another bi-directional tape applicator head is described for dispensing and compacting tape to opposite directions onto a working surface. This second known tape applicator head includes a rotation rack assembly onto which the two dispensing blocks are mounted to be stationary relative to each other but to shift their positions in unison relative to the remainder of the head at the end of the tape laying pass. This movement of the dispensing blocks produces a step-over, or loop, in the tape at the end of each tape laying pass which prevents distortion of the tape as the tape is folded back on itself during reversal of the tape placement direction. Also, the dispensing block which is not engaged with the tape as the head is moved in a particular one of the two opposing directions, is spaced a predetermined distance from the working surface, to eliminate the possibility of this block engaging the end of a previously laid tape layer. Also, in this tape applicator head, the tape may be fed onto the working surface in any direction, horizontal or vertical.
However, this last mentioned known tape applicator head does not include tape feeding and shearing mechanisms. Consequently, this tape applicator head is best suited for laying up laminated parts from a continuous length of composite tape, which is folded back on itself on reversal of tape-placement direction rather than forming contoured laminated parts requiring a plurality of different lengths of tape.
In these applicator heads, the tape is either unidirectional or X-ply, i.e., the tape filaments are parallel to the longitudinal axis of the tape (unidirectional) or inclined at an angle to the longitudinal axis of the tape (X-ply).
For those structures which only require one type of tape (unidirectional or X-ply), the applicator heads noted above are well suited. Many times, however, a structure requires both types of tape. In this event, the applicator heads noted above are not entirely satisfactory because of the need to change and re-thread the tape head with the different type of tape.